Firearms that shoot small caliber rimfire cartridges enjoy great popularity because the cost of the firearm and attendant ammunition cost less than center fire firearms. Rimfire cartridges are typically on the lower end of kinetic energy because the velocity of the projectile is generally about 1100 feet per second or less. The lower projectile velocities have historically prevented small caliber rimfire cartridges from being used for anything but small game and at ranges under 100 yards.
Attempts to increase the speed of small caliber projectiles has been limited by both the bullet casing metal thicknesses as well as problems associated with firing thicker bullet casings. Thicker bullet casings require a heavier main spring for discharging the cartridge. Because of the need for a heavier main spring, the uplift force required to operate the bolt can be prohibitive. In addition, the heavier main spring produces significant drag as the user rotates the bolt handle to compress the main spring. As a result, the commercial success for such firearms and ammunition has been limited.
Also, because conventional small caliber rimfire firearms are not used for distances greater than about 100 yards, there has been little interest in developing higher quality trigger mechanisms suitable for longer distance shooting. Triggers for firearms must strike a compromise between ease of use and safety. Triggers utilized in competition firearms eliminate or reduce trigger creep by reducing the amount of sear engagement. As used herein, the term “creep” generally refers to the distance that a trigger will travel, or must be pulled, before the sear is engaged and dropped, thus permitting the main spring and firing pin to discharge the firearm. In addition, the “feel” of the trigger may be improved by polishing the engaging surfaces of the sear and the trigger. However, polishing does not reduce the amount of trigger creep, just the “feel” of the trigger creep. On the other hand, a reduction in the amount of sear engagement results in a perceived better trigger pull. For example, a trigger having about 0.015 inches of engagement would be considered by most shooters to be a better trigger than a trigger having about 0.025 inches of engagement.
An engagement between the sear and the trigger of greater than about 0.020 inches generally results in a trigger that is safe from accidental firing during an impact event (e.g., jarring or dropping the firearm), but the trigger is also generally considered to be prohibitively heavy. Reducing the sear and trigger engagement to about 0.016 inches results in a more favorable trigger creep, but the firearm is more prone to accidental discharge in an impact event.
For rifles having a heavy or high-force main spring, conventional small caliber bolt action firearms can be limited by the amount of force required to actuate the bolt.
Thus, a bolt action firearm having a low creep safety trigger and capable of actuating heavier main springs while, at the same time, providing improved trigger pull and which in one embodiment may be field adjustable by the user would be welcomed.